Method for Creating Controlled Atmospheres without Containment on Automated Packaging Lines

ABSTRACT

A method and an installation seeking to create a controlled atmosphere in the head space of a product storage container in an installation of the type in which the following measures are taken continuously: —the container is partially filled with the product to a given fill level; —the upper part of the container is placed in contact with a treatment gaseous atmosphere aimed at removing all or some of the air present in the container above said fill level and at installing the required controlled atmosphere above said level; —the upper edge of the container is sealed or closed using a suitable means; —the controlled atmosphere being installed upstream of and/or during sealing, characterized in that the controlled atmosphere is installed in an uncontained injection zone by using at least one injector of tubular type oriented in the injection zone in such a way that at least one of the components of the velocity of the sprayed gas is the opposite to the direction of travel of the containers, and in that the injector is supplied with flow that is turbulent.

The present invention concerns the field of methods for creating modified atmospheres on articles or products, food or otherwise, in automated production lines. “Modified atmosphere” means an atmosphere different from the ambient air; for example the inerting of the head space of bottles or containers containing a liquid at the time of or a little before the placing of the stopper.

Hereinafter the expressions “head space” or “gaseous canopy” will be used indifferently, a concept well known to persons skilled in the art of the packaging of products, in particular food, drink and cosmetic products, as designating the space situated above the level of liquid in the container (as far as the top neck receiving the final closure means).

As a general rule, the invention concerns the bottling or packaging of any type of product requiring a modified atmosphere to protect it against the takeup of oxygen, moisture, air pollutants and other dusts. The following examples can be cited:

-   -   Bottling of drinks (for example fruit juice, vitaminised drinks,         wine, mineral waters, etc.)     -   Bottling of oils (food or otherwise)     -   Putting cosmetics (for example cream, shampoo, essential oils,         etc.) in flasks, bottles or various containers     -   Putting various products in the health field (for example         ointments, creams, vaccines, active ingredients, ferments, etc.)         in flasks, bottles or containers     -   Preserving foodstuffs     -   Packaging paints in pots     -   Packaging flammable products (petrol, solvents, etc.)     -   etc.

The creation of modified atmospheres consists, normally, of a partial containment in the form of a tunnel in which the treatment gas (nitrogen for example) is injected. The majority of systems are equipped with gas jets in order to discharge the air from the head space that is replaced by the atmosphere of the tunnel. The containers or bottles travel on a conveying system inside the tunnel.

The conveyors may be of very different technologies such as continuous-movement belts, back-step conveying systems, circular-movement conveyors of the carousel type, etc.

These existing technologies already give good results for many cases but may have drawbacks (see be unable to achieve the required specifications) in certain technical situations:

-   -   when the conveying speeds are high; for example for a production         line for 50 cl drinks bottles, the rate reaching 40,000 bottles         per hour and the conveying speed may be as much as 1.6 m/sec.         The time necessary for emptying the air and then filling the         head space requires a fairly long tunnel length of around 50 to         70 cm or even 1 m. The longer the tunnel the better the quality         of the atmosphere in the head space will be (in terms of         residual oxygen achieved for example);     -   the choice of an inerting tunnel may represent a problem in some         cases, or even a dangerous situation during incidents downstream         thereof, for example where the stopper is picked up. Such         collisions in cascade with the impossibility of ejecting the         bottles because of the presence of the cover may cause the         bursting or detachment of the cover, the loss of the bottles and         significant stoppages in production;     -   in the food field the cleanliness constraints are great and         require periodic and frequent stoppages to clean and aseptisize         the lines. The tunnels then represent additional contamination         risks and therefore increase the line cleaning times because of         the difficulties in contamination that they generate;     -   the choice of these tunnel technologies moreover presents         another drawback: it is not possible to treat the         stopper-gripping phase. In general terms, over a short distance,         which may be up to 20 cm, between the end of the tunnel and the         placing of the stopper, the containers or bottles move in air.         In this interval, the nitrogen contained in the head space is         gradually evacuated and is replaced with air. This phenomenon         may prove to be of major importance when the conveying speed is         fast and the distance between the end of the tunnel and the         gripping of the stopper is great;     -   faced with this, the solution that would consist of treating         until the stopper is gripped cannot be envisaged since the         machines placing the stoppers cannot be included in the tunnel         because of the dimensions and technologies of these machines.         The placing of the stoppers is therefore carried out in air and         it is in practice currently considered, in existing         installations, that the atmosphere of the head space created         upstream remains satisfactory, despite the inevitable partial         mixing with ambient air.     -   It is deduced from this that the oxygen contents will be all the         higher, the greater the production rates, they may be as much as         10%, and that the residual oxygen levels in the head space are         difficult to reproduce.

It is therefore understood that it would be advantageous to be able to have a novel solution for establishing such modified atmospheres, meeting specific specifications, in particular in the case of very high conveying rates.

As will be seen in more detail hereinafter, the present invention sets out to propose a novel solution for achieving the treatment without containment.

This solution was in particular designed by noting that the movement of the bottles naturally assists the discharge of the atmosphere from the head space.

Considering the pressure in the head space as a reference (atmospheric pressure or substantially at this level), the moving bottle is subjected to a slight overpressure on the front part and to a slight negative pressure on the rear part.

This naturally causes a movement of the atmosphere: the atmosphere is discharged through the rear and is replaced by air from the front (illustration of this phenomenon in the accompanying FIG. 1).

It is therefore wished, by virtue of the present invention, to offer a configuration for:

-   -   profiting from this phenomenon by ensuring that the atmosphere         situated in front of the container is a required suitable         atmosphere, for example nitrogen. In this case, the discharge of         the initial atmosphere from the head space (which may be air)         takes place naturally through the rear, and is replaced by the         treatment atmosphere present in front of the container, for         example blown nitrogen, projected in the opposite direction to         the movement of the containers in the installation;     -   maintaining the required atmosphere, for example nitrogen, on         the front face of the container until the stopper or other means         of closing the top neck downstream is placed;     -   at least one injector is used, the sizing of which is a very         important element of the present invention, this will be         returned to later, which is used to produce the gas flow or jet.         At least one but preferentially two injectors positioned on         either side of the conveyor and oriented in the opposite         direction to the movement of the containers or bottles will be         used.     -   The injector consists for example of a tube, with a preferably         square, rectangular or circular cross section (but this is         merely illustrative), as will have been understood the objective         of the invention is to work without any containment measures,         the gas sprayed through the injector or injectors therefore         emerges in the ambient air surrounding the zone to be treated.     -   The direction of the gas flow or jet is therefore such that at         least one of the components thereof is in the opposite direction         to the direction of movement of the containers or bottles.

In this application “top edge” or “opening neck” of the container will be spoken of, which must be understood, as will be clear to a person skilled in the art, as the top opening of the container through which the filling takes place, before this container is of course closed by any means at the end of the line.

The present invention therefore concerns a method aimed at creating a controlled atmosphere in the head space of a container for storing a product, in a moving installation of the type where the following measures are implemented:

-   -   the container is partially filled by means of a product up to a         given filling level;     -   the top part of the container is put in contact with a gaseous         treatment atmosphere, aimed at evacuating all or some of the air         present in the container above said filling level and to put in         place, above said level, the required controlled atmosphere;     -   the top edge of the container is sealed or closed using a         suitable means;     -   the establishment of the controlled atmosphere being achieved         upstream and/or during sealing;     -   characterised in that the controlled atmosphere is established         in an unconfined injection zone, by the use of at least one         tubular-type injector, able to spray towards the top edge of the         container in the injection zone, the gaseous treatment         atmosphere, and oriented in the injection zone so that at least         one of the components of the velocity of the projected gas is         opposite to the direction of movement of the containers, and in         that the injector is fed with a gas flow making it possible to         achieve a turbulent flow regime with a Reynolds number of         between 5,000 and 20,000.

Injection therefore takes place in an unconfined space, without a tunnel, without hooding, in the open air, by means of the special conditions adopted.

As indicated above, the controlled atmosphere is established upstream of and/or during sealing.

The rapid movement of the containers in certain production sites is thus taken account of, for which it is necessary to limit the space available before closure and once the control atmosphere has been achieved, otherwise the air will once again enter the container, and hence the fact that, according to circumstances, the injection will take place just before and/or during the placing of the cap, stopper or lid, and therefore as required before and during closure, or during the actual closure.

The present invention also concerns an installation for the continuous packaging of a product in storage containers, of the type where the following measures are taken:

-   -   the container is partially filled with the product to a given         fill level;     -   the upper part of the container is placed in contact with a         treatment gaseous atmosphere aimed at removing all or some of         the air present in the container above said fill level and         establishing, above said level, the required controlled         atmosphere;     -   the upper edge of the container is sealed or closed using a         suitable means;     -   the controlled atmosphere being established upstream of and/or         during sealing,     -   characterised in that the controlled atmosphere is established         in an unconfined injection zone, which is provided with at least         one tubular-type injector, able to spray the gaseous treatment         atmosphere towards the top edge of the container in the         injection zone, said at least one injector being oriented in the         injection zone so that at least one of the components of the         velocity of the sprayed gas is opposite to the direction of         movement of the containers.

Other features and advantages of the present invention will emerge more clearly from the following description given for illustrative purposes but in no way limitatively, made in relation to the accompanying drawings, for which:

FIG. 1 is a schematic illustration of the phenomena occurring naturally during the movement of the containers (i.e. movement of the internal atmosphere (head space) towards the rear and replacement thereof with air situated on the front face of the container).

FIG. 2 is a schematic illustration of the phenomena that are established by means of the conditions of the present invention.

FIG. 3 gives a schematic representation of an injector used for the assessment work carried out by the applicant, a figure in cross section where the main parameters taken into account are mentioned.

FIG. 4 is a partial schematic representation of an embodiment of the invention.

FIG. 5 is a partial schematic representation of another embodiment of the invention.

The phenomena illustrated by FIGS. 1 and 2, amply explained in the above description, will not be repeated here.

FIGS. 4 and 5 give a clear view of two embodiments of the invention.

In both cases the containers can be clearly seen (already containing product) conveyed to a station for sealing or closing by any suitable means (stopper, screw cap, etc.).

In an injection zone situated at a very short distance upstream of the sealing station (according to the invention it is preferred not to exceed 20 cm), the containers encounter the gas jets sprayed under flow-rate and sizing conditions in accordance with the invention by two injectors, positioned on either side of the conveyor and oriented in the opposite direction to the movement of the containers or bottles:

FIG. 4 illustrates a case where the two jets are directed towards the same area of the conveyor.

FIG. 5 illustrates an embodiment where the two jets are directed onto areas of the conveyor that are slightly offset, which makes it possible to involve a greater conveyor length and therefore to have more time for removing the air from the head spaces.

The work conducted by the applicant (both experimental and modelling) showed that, in such a configuration of injection in front of the containers, the quality of the atmosphere established in the head space (for example the residual oxygen level achieved in the head space) will be influenced by the following parameters:

-   -   the packaging time, that is to say the time necessary for         completely effecting the transfer of the atmosphere of the head         space and replacement thereof by a suitable atmosphere. This         time is itself dependent on:         -   the blowing speed of the atmosphere in the opposite             direction, for example nitrogen,         -   the speed of movement of the containers (in the direction             opposite to the blowing),         -   the distance available between the blowing of the gas and             the gripping of the stopper (or other closure means),         -   the volume of the head space;     -   the residual oxygen content in the sprayed gas flow (for example         nitrogen), sent onto the front edge of the bottle or container.

And precisely the applicant carried out work for studying the parameters influencing the oxygen content of the nitrogen flow sprayed onto the containers, the objective being to promote conditions that minimise the mixing of the sprayed atmosphere with the ambient air.

This work showed that the parameters having an influence on the oxygen content in the nitrogen flow are:

-   -   the distance between the injector and the zone to be treated     -   the velocity of the treatment gas     -   the flow regime     -   the position of the relevant point of the jet with respect to         the centre of the jet     -   the cross section of the gas jet or flow with respect to the         surface to be treated.

In order to remove any ambiguity, “surface to be treated” is spoken of in the present application to designate the cross section of the “opening neck” of the container, i.e. of the top opening of the container through which the product filling takes place.

This work was therefore carried out using the following parameters,

-   -   tubular injector of diameter D     -   inerting distance between the injector and the surface to be         treated: H     -   nature of the sprayed gas: nitrogen     -   velocity of the gas: v     -   distance of a relevant point inside the jet from the centre of         the jet: d

(These parameters are displayed in the accompanying FIG. 3).

The results observed can be summarised as follows.

1—Influence of the distance H (between the injector or injectors and the surface to be treated)

Various evaluations have been made with a tubular injector with a diameter of 44 mm and for various gas velocities in turbulent flow regime (2, 4, 6 and 8 m/s). They show clearly that the distance parameter between the injector and the zone to be treated has a great influence on the oxygen content observed at the centre of the jet:

-   -   the residual oxygen content obtained increases with the distance         for a given velocity     -   it is necessary to increase the velocity in order to maintain         the level of oxygen when the injector is moved away from the         surface to be treated     -   for small distances (e.g. 5, 10 cm) the atmosphere remains very         correct (100 ppm and less) whatever the velocity of the jet.

It is nevertheless known that in practice it is rarely possible to position the injector or injectors very close to the container because of the size of the stopper-placing machine. It is then sometimes necessary to move the injection station away from the stopper-placing zone, even if the best efforts are made to keep a minimum distance, in order to obtain an atmosphere above the liquid that does indeed correspond to the specification, for a minimised gas consumption.

As will be detailed more clearly below, it is preferred according to the invention not to exceed a distance of 20 cm, or even more preferentially not to exceed a distance of 15 cm for the most severe residual oxygen (or other pollutant) specifications.

This is because, according to preferred embodiments of the invention, a distance between the injector and the zone to be treated of less than 20 cm will be used (in particular, depending on the specifications of each site, for residual content objectives of less than 2%) and more preferentially less than 15 cm (in particular for content objectives of less than 1%).

2—Influence of the flow regime

The influence of the gaseous regime for a tubular injector with a diameter of 30 mm and a distance H of 15 cm was evaluated, by means of a reading of the oxygen contents at the centre of the jet according to the Reynolds number.

The Reynolds number is expressed by:

-   -   R=ρ v D/μ where     -   ρ=density (kg/m³)     -   v=velocity of the gas (m/s)     -   D=diameter of the injector (m)     -   μ=dynamic viscosity (Pa s).

This work shows that it is desirable to avoid the transient regime between laminar and turbulent, where the oxygen content is very high (reaching 3%).

The Reynolds formula shows the involvement of the velocity on the one hand and the diameter on the other hand: it then proves to be very difficult, in particular for fairly high diameters (>50 mm), to remain stable in laminar regime, the velocities then having to be very low, the flow rates low and therefore the packaging time greater and the distance to the injector very small.

It is consequently preferred according to the invention to be positioned in turbulent regime, where 5,000<Re<20,000, preferring nevertheless relatively low velocities in order to limit the consumptions of gas.

3—Influence of the diameter of the injector

Curves for oxygen contents in the jet were established, according to the distance from the relevant point to the centre of the gas jet, for various gas velocities, under the following conditions:

-   -   D=44 mm     -   H=20 cm     -   v=1, 2, 5 or 10 m/s.

The following conclusions appear to be able to be drawn:

-   -   For the value of H fixed here (20 cm) the low velocities (1 and         2 m/s) do not give satisfactory atmosphere performances         (residual oxygen content greater than 4%).     -   A degradation of the residual oxygen content is also noted as         soon as the relevant point in the jet moves away from the centre         of the jet.     -   For a zone where it would be wished to treat with a maximum of         2% residual oxygen, it was necessary not to exceed (for the         context of diameters tested here of course) a diameter of 22 mm.

Without in any way being bound by the attempts at technical explanation that follow, it can be reasonably thought that, when moving away from the centre of the jet, by venturi effect there is suction of the air around the jet that then impacts more greatly on the outside of the jet in contact with the air than inside this jet. And it can be thought that the extent of the external layer of the jet that will be impacted by the venturi effect is related to the velocity of the gas (and therefore to the Reynolds number), the higher the velocity the thicker the impacted layer while for small jet diameters or very high velocities a large part of the jet could be contaminated by the external air.

In this context, according to the specification of the production site, it will be preferred according to the present invention to adopt sizings where the dimensions of the injector are appreciably greater than the dimensions of the zone to be treated, and in particular where the cross section of the injector is at least twice as great as the surface area to be treated, and even more preferentially at least three times greater.

Tests on the bottling of drinks of the fruit juice type were carried out in accordance with the present invention, under the conditions summarised below:

-   -   PET plastic bottles     -   Content 0.5 litres, Diameter of neck=32 mm     -   Line rate=40,000 bottles/hour     -   Inerting objective: <5% residual oxygen in the gaseous canopy         above the liquid     -   Two offset injectors used, diameter 76 mm     -   Flow rate: 100 Nm³/h per injector     -   Distance between injector and necks=15 cm

Under these conditions a residual oxygen content of around 2% is then obtained, which perfectly meets the specification fixed by the site.

It is necessary to indicate that, by means of a comparative prior method (inerting tunnel 1 metre long, with 100 Nm³/h of inerting gas consumption) it was not possible to drop below 8% residual oxygen. 

1-6. (canceled)
 7. A method for producing a controlled atmosphere in a head space of a container storing a product, the containers moving in an installation, said method comprising the steps of: partially filling the container with a product up to a given filling level; putting a top part of the container in contact with a gaseous treatment atmosphere in an unconfined injection zone, thereby evacuating some or all of any air present in the container above the filling level and putting the gaseous treatment atmosphere in place above the filling level, wherein the gaseous treatment atmosphere is put into place using at least one tubular-type injector that sprays the gaseous treatment atmosphere towards a top edge of the container in the injection zone, the injector being oriented in the injection zone so that at least one component of a velocity of the sprayed gas is opposite to a direction of movement of the containers in the installation, the gaseous treatment atmosphere sprayed from the injector in a turbulent flow regime with a Reynolds number of between 5,000 and 20,000.
 8. The method according to claim 7, wherein a diameter of the injector is such that the cross section of a jet of the sprayed gaseous treatment atmosphere is greater than twice a surface area of the container to be treated.
 9. The method according to claim 7, wherein a diameter of the injector is such that the cross section of a jet of the sprayed gaseous treatment atmosphere is greater than three times a surface area of the container to be treated.
 10. The method according to claim 7, wherein a distance between the injector and the injection zone is less than 20 cm.
 11. The method according to claim 10, wherein a distance between the injector and the injection zone is less than 15 cm.
 12. The method according to claim 8, wherein a distance between the injector and the injection zone is less than 20 cm, and preferentially less than 15 cm.
 13. The method according to claim 12, wherein a distance between the injector and the injection zone is less than 15 cm.
 14. The method according to claim 7, wherein said at least one tubular-type injector comprises first and second tubular-type injectors each one of which is positioned on either side of a conveyor conveying the containers partially filled with product.
 15. The method according to claim 7, wherein the unconfined injection zone is not confined by a hood or tunnel.
 16. The method according to claim 7, wherein the product is fruit juice.
 17. The method according to claim 7, wherein the gaseous treatment atmosphere is nitrogen. 